In the past, in order to improve the performance of general aviation aircraft, considerable effort has been exerted in the field of airframe design, particularly in the area of wing design, from which substantial performance improvements have resulted.
On the other hand, for propellers or air screws, the main task of which is to transform the power supplied by the engine into propulsion, one has not learned of any very successful activities. The output of propellers has in the past been improved only insignificantly, although this type of drive has a thrust potential that could be utilized much more.
Propellers now in use achieve, as they have done unchanged for a long time, only about 50 to 70% on the ground and about 90% when cruising, of the propeller thrust values maximally possible according to the impulse theory.